Certain shoes have a wedge or other type of insert in their heel portions. Often, a wedge insert is used to elevate the shoe's heel. Conventionally, such a shoe is constructed by cutting out different layers that ultimately will make up the shoe's sole (i.e., the portion of the shoe that is beneath the wearer's foot) and then bonding those layers together using an adhesive material. However, prior to bonding two of such adjacent layers together, a wedge of the desired shape is inserted at the back of the shoe between such two adjacent layers. Then, instead of bonding the upper and lower layers directly together along their entire surface areas, the upper layer is bonded to the top surface of the wedge and the lower layer is bonded to the bottom surface of the wedge. For the portion of the shoe that is forward of the wedge, the two adjacent layers generally are bonded directly to each other.
Once all of the foregoing steps have been completed, the sides of the shoe's sole are ground down, in order to smooth out any sections where the layers do not match precisely, to de-emphasize any seams between the layers (e.g., to provide the appearance of a single non-layered material), and to provide any desired shaping of the sole's side surfaces (e.g., to provide rounding, grooves or other three-dimensional patterns).
However, the present inventors have discovered that, when using the conventional production technique described above, because a significant portion of the insert's side walls also are exposed, the grinding of the layers comprising the shoe's sole almost necessarily results in grinding at least a portion of the inserted wedge. That is, even manual grinding usually cannot be limited strictly to the other layers of the shoe's sole; some of the grinding will overlap onto the sides of the insert. Any attempts to prevent such overlap generally would require extreme care that would substantially increase the cost of the finished product and, therefore, would be unfeasible for mass, medium-scale or large-scale production. The end result is that at least some portion of the inserted wedge (e.g., along its bottom and top edges) also will be ground down.
For some shoes, this result is acceptable or even desirable. The best example of such a case is where there is a desire for the shoe's heel to have a uniform appearance, i.e., so that there is no indication that the heel is in fact comprised of multiple layers and a separate wedge. Depending upon the type of grinding surface that is used, the side walls of the shoe's heel will appear to be uniformly smooth or textured.
However, the present inventors have discovered that such a manufacturing technique limits the types of wedges and other inserts that can be used within a shoe's sole, as well as the variety of shoe designs that can be made with an insert. For example, using such a conventional technique generally precludes one from inserting a decorative wedge, or at least one that has a fully decorated outer surface, because the subsequent grinding generally would obliterate such surface decorations. At the same time, simply omitting the grinding step generally would have the undesirable effect of leaving intact any production imperfections that exist after the individual layers have been bonded together.